Is mirror...?

I have installed 2 servers - ns1 and ns2 (both DNS, www, DB, mail,...) using perfect server ... on debian 6 tutorials. I didnt use gluster fs, but did use expert option when installing ISPConfig 3 on ns2. At the end I wanted ns2 to be secondary DNS server for ns1, so i enabled the DNS-Server checkbox and selected ns2 server "is mirror of Server" ns1. What about other checkboxes (web, mail,...)? Should I enable them also or not (because i didnt install gluster), can i use mail, web,... services on both ns1 and ns2 if i have chosen "ns2 is mirror of ns1"...?
I'm still a newbie here, so i would be very gratefull for any advice.